Effect of lectins and chemical modification on the hemagglutinin activity of human plasma fibronectin.

Purified human plasma fibronectin has been shown to agglutinate protease-treated red cells [Vuento, Hoppe-Seyler's Z. Physiol. Chem. 360, 1327-1333, (1979)]. The present report shows that the activity is inhibited by low concentrations of lectins and by macromolecular serum factors. Chemical modification of carboxyl groups of fibronectin strongly inhibited the activity, but modification of amino groups of guanidinium groups had little effect on the activity. The results suggest that fibronectin receptors on erythrocyte surface are carbohydrate-containing molecules. Humoral macromolecular factors may control the interaction of fibronectin with cell surfaces. Chemical modification studies indicate that the parts of the fibronectin molecule responsible for the hemagglutinin activity are different from those mediating the binding of fibronectin to collagen.